Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$237.81	7.784%	$256.3211	$256.32	$256.30	$256.30
Purchase #2	$124.33	4.563%	$130.0032	$130.00	$130.00	$130.00
Purchase #3	$115.96	12.431%	$130.375	$130.38	$130.40	$130.40
Purchase #4	$81.34	9.342%	$88.9388	$88.94	$88.95	$88.90
Purchase #5	$151.91	13.543%	$172.4832	$172.48	$172.50	$172.50
Purchase #6	$126.52	8.218%	$136.9174	$136.92	$136.90	$136.90
Purchase #7	$194.35	10.787%	$215.3145	$215.31	$215.30	$215.30
7 purchase totals =	$1,032.22		$1,130.3532	$1,130.35	$1,130.35	$1,130.30